The strange thing is that the "reopened" files are created but all output still goes to the first one.

Probably a Windows issue...

Ok got it. I'm pushing new file handles onto the @FH array, but only the first 3 ones are written!

The trouble with overly clever one liners... 🤦🏻‍♂️

Try putting open ..., '>', $_ for split scalar <> or similar in a BEGIN block, instead of running it on each loop iteration. :-)

> instead of running it on each loop iteration. :-)

see Re: Split tab-separated file into separate files, based on column name

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}